1. Field of the Invention
This invention relates to an improvement in a differential mechanism being arranged to prevent misassembling thereof.
2. Description of the Related Art
A differential mechanism comprises a gear assembly disposed between two drive shafts for permitting one shaft to turn at a different speed from the other, while transmitting power. An example differential mechanism is disclosed in International Publication No. WO 95/00777 xe2x80x9cDIFFERENTIAL MECHANISMxe2x80x9d.
The disclosed differential mechanism comprises an input housing having a plurality of grooves formed in an inner peripheral surface of the housing, and a plurality of two different types of cam followers disposed Internally of the housing. The cam followers include elongate drive dogs formed integrally there with for engaging in the grooves. The drive dogs of the cam followers of one type have grooves for distinguishing that type from another. When they are fitted into the input housing, the cam followers are arranged In an annular array such that two of the drive dogs with the distinguishing grooves and two of the drive dogs without such grooves are positioned alternately in close proximity.
In the disclosed differential mechanism thus arranged, for the condition of assemblage, it must be confirmed through the eyes of an attendant whether the drive dogs have the grooves or not, whereupon a misjudgment or an oversight may occur, thereby causing misassembling of the cam followers.
To cope with this problem, one may propose to conduct an operation test, after completion of the differential mechanism, on all of the cam followers to confirm whether misassembling occurred in the mechanism. However, such a proposal is not a panacea in that it requires additional man hours, thereby deteriorating the productivity.
It is therefore an object of the present invention to provide a differential mechanism which is arranged to prevent misassembling of the mechanism with increase surety.
According to an aspect of the present invention, there is provided a differential mechanism which comprises: a differential case assembly having a casing body connected to a source of drive force and a cap member coupled with the casing body to cover one opened end of the casing body; a plurality of input blocks housed in the case assembly and being movable circumferentially of the case assembly in correspondence with rotation of the casing body; a pair of output cam members for clamping the input blocks relatively slidably and being independently rotatable owing to a frictional force produced with respect to each of the input blocks to thereby independently rotatable owing to a frictional force produced with respect to each of the input blocks to thereby initiate a differential motion on an output side of the differential mechanism; the input blocks being provided in at least two different types and having projected portions, the projected portions of the input blocks of one type having a first upper end width, the projected portions of the input blocks of another type having a second upper end width different from the first upper end width; and the casing body having first and second axial grooves formed on an inner peripheral surface thereof such that they extend axially of the differential mechanism, the axial grooves being shaped complementarily to the projected portions of the input blocks for meshing engagement therewith.
With this arrangement, it becomes possible to surely prevent misassembling of the input blocks with the casing body. This leads to the further advantage that extra man hours, required in reassembling after misassembling is found, can be avoided, thereby increasing productivity.
Desirably, the input blocks are arranged in an annular array such that two of the input blocks of one type and two of the input blocks of another type are positioned alternately. It is also desirable that two of the first axial grooves and two of the second axial grooves are positioned alternately in correspondence with the input blocks.
Preferably, the axial grooves of the casing body have a substantially trapezoidal cross section. The first upper end width of each of the projected portions of the input blocks of one type may be larger than the second upper end width of each of the projected portions of the input blocks of another type.
Each of the second axial grooves may be provided with a projection at a bottom thereof while each of the projected portions of the input blocks of another type may be provided on an upper surface thereof with a recessed portion shaped complementary to the projection.